There is an increasing concern with the number of accidents at railroad crossings. Collisions with trains are generally catastrophic, in that the destructive forces of a train are usually no match for any other type of vehicle. Indeed, federal and state regulations require that many types of vehicles, termed xe2x80x9cpriority vehiclesxe2x80x9d, take special precautions before crossing a xe2x80x9cgradexe2x80x9d railroad crossing. For example, school buses, hazardous cargo carriers and other emergency vehicles are often required to stop at railroad crossings and verify the absence of an oncoming train before proceeding. A xe2x80x9cgradexe2x80x9d railroad crossing is where a motor vehicle highway, street or road directly intersects a railroad track. An intersection of a highway and a train track that involves an overpass is not a xe2x80x9cgradexe2x80x9d crossing, as no collision would occur even if the vehicle and train arrived at the same location at the same time.
The safety at railroad crossings has become of such significance that new federal agencies and studies have been undertaken to improve the grade crossing safety procedures. In view that a substantial number of fatalities occur every year due to collisions with trains, there has been an increased endeavor to provide sensors and detectors to warn oncoming traffic of the proximity of an approaching train. U.S. Pat. No. 5,739,768 describes a train proximity detector that provides a sensory indication to an operator when the vehicle and the train are located proximate each other. The train proximity detector of such patent receives the unique frequency transmitted by the train from the head end to the last car thereof The carrier frequency transmitted by the train is decoded to identify certain data in the frame of transmitted data to thereby verify that the transmission originated from a train. While the train proximity detector functions very efficiently for its intended purpose, the operator of the vehicle will be given a warning of the proximity of the train, even if the train and vehicle are not on a collision course. For example, if the train and the car are traveling together, but in parallel paths, and there is no intersection between the road and the railroad track, the operator of the vehicle is nevertheless warned about the proximity of the train.
Other suggested devices attempt to overcome this problem, but at the expense of additional complexity, cost and apparatus that is required to be added to the equipment of the train. For example, in U.S. Pat. No. 4,942,395, by Ferrari, the train transmits on a first frequency to a receiver located at an intersection, and a second frequency is transmitted from a transmitter at the crossing to oncoming vehicles. In this manner, the vehicles do not directly receive the train transmission, and the vehicles are only provided a warning when in the proximate vicinity of the railroad crossing.
U.S. Pat. No. 5,554,928 by Shirkey et al. discloses a wireless train proximity alert system in which both a locomotive and vehicle rely on GPS coordinates for proper operation. In this system, the locomotive computes the train speed based on the GPS coordinates and transmits the coordinates and the train speed to a grade crossing transceiver. The grade crossing transceiver receives such information and computes an estimated time of arrival of the train. When the estimated time of arrival is within about 20-30 seconds of the grade crossing, the grade crossing transceiver transmits the coordinates of both the crossing and a boundary warning zone. A receiver mounted in a vehicle receives the coordinates of the grade crossing as well as the coordinates of the boundary warning zone around the grade crossing. In addition, the vehicle itself has a GPS receiver for receiving the coordinates of the vehicle. A controller determines if the vehicle is then within the boundary of the warning zone. If so, the controller determines if the vehicle is within a predetermined range of the crossing and if so, an alarm signal is provided. The predetermined range calculated by the vehicle controller is dependent upon vehicle speed and the braking distance of the vehicle which is a function of the type of vehicle.
Many other types of vehicle and train proximity detectors are proposed in the prior art. Many of the proposed techniques involve complicated and expensive equipment that must be added either to the train or to the vehicle, or both. It can be appreciated that in order for train proximity detectors to be installed on vehicles, in general, the equipment must be efficient, reliable and cost effective.
From the foregoing, it can be seen that a need exists for an improved train proximity detector that utilizes currently available resources to provide an operator of a vehicle with a sensory indication when the vehicle is in the vicinity of the train, and on a collision course therewith. Another need exists for an improved train proximity detector that relies on the presence of a train by conventional transmissions therefrom, as well as relies on global positioning satellite (GPS) data for determining the location and direction of travel of the vehicle, whereby when such data is processed, it can be determined whether the vehicle is on a collision course with the train. A subsidiary need exists for a train proximity detector that has available data identifying each grade railroad crossing and corresponding compass bearing data of the roads crossing the railroad track.
In accordance with the principles and concepts of the invention, there is disclosed an improved train proximity detector that substantially reduces or overcomes the problems and disadvantages of the prior art devices.
In accordance with a preferred embodiment of the invention, disclosed is a train collision avoidance system that not only determines if a train is in the vicinity of the vehicle, but also if the train and the vehicle are both moving toward a common intersection where a collision would be inevitable. In the preferred form of the invention, the train collision avoidance system includes a first processor for receiving GPS longitude/latitude parameters to define the location of the vehicle. The first processor also includes as an input a compass or bearing for providing the direction of travel of the vehicle. Lastly, the first processor has access to a data base memory storing railroad grade crossing locations. The grade crossing location data stored in the data base is associated with heading or bearing information of all roads that intersect the railroad tracks. Operating in conjunction with the first processor is a second processor that detects the proximity of the train. The second processor is fully disclosed in U.S. Pat. No. 5,739,768, and is coupled to the first processor by an I/O bus. The train proximity detector is sensitive to train transmissions within about at least 1500-2000 feet from the train.
The GPS longitude/latitude coordinates of the vehicle are processed by the first processor to undergo a ranging function. The ranging function involves the elimination of various least significant digits of the longitude and latitude coordinates, thereby providing an area of protection around the vehicle of, for example, 800 meters. Next, the first processor searches through the data base memory to find all the grade crossing locations that fall within the protection area situated about the vehicle. If no affirmative grade crossing is found in the data base, then the first processor continues by receiving another GPS longitude/latitude coordinate and compass bearing parameter and undergoes the same processing. If a grade crossing is found in the data base memory to be within the area of protection around the vehicle, then the first processor determines if the vehicle is on the same heading as the road that intersects the railroad tracks. This is accomplished by comparing the vehicle bearing with the direction data stored in association with the grade crossing data stored in the data base. If a match is found as a result of this second comparison, a signal is provided on the I/O bus connected to the second processor. The second processor is programmed to determine if a train is in the proximate area of the vehicle by sensing whether any train is transmitting on its allocated frequency. If no train is transmitting on its frequency, then a first level, or alert indication is provided to the operator of the vehicle. In the event that the second processor has indeed detected the presence of a train in the vicinity of the vehicle, then a second level, or warning is provided to the operator of the vehicle. The first and second levels constitute different visual and audible signals to the vehicle driver to provide the requisite significance of the situation.
In other variations of the invention, the area of protection about the vehicle can be a function of the speed of the vehicle. In other words, if the vehicle speed is greater than a threshold speed, then the area of protection automatically increases.